THIS is not Miami. In case the Knicks had any thoughts that the road to the Finals would be a South Beach breeze, they learned last night that the Pacers are much different than the Heat.

The Pacers score. Lots of them score.

Against the Heat, the Knicks got stupid too many times, but were able to survive despite themselves. They can’t suffer such brain drains against the Pacers. Stupid loses in this series – and that’s what happened to the Knicks last night in their 102-88 hammering in Game 1 at Conseco Fieldhouse.

Stupid like this: The Knicks cannot afford to muscle-pose as Latrell Sprewell did after his manly jam brought them to 71-68 – and then get beat on the other end of the floor by Jalen Rose for a dunk because Sprewell failed to get back.

Sprewell admitted he erred: “I probably could have gotten back if I hadn’t been showboating so much,” he said, “but somebody has to help out, too. It’s a team game.”

Chris Childs cannot afford to make a dumb reach-around foul early in the fourth, when the Knicks are down seven with Travis Best 30 feet from the basket and the shot clock about to expire. Larry Johnson cannot do the Big L when the Knicks are 16 points down in the second quarter.

It’s one thing to give the Big L in a close game. It’s another to do it when you’re down by two touchdowns and a safety. Then, the L stands for Loser. Johnson was pathetic all night, scoring three points while his counterpart, Dale Davis, pumped in 14. That Dumb L also gave the capacity crowd more juice. On the road, you try to take the crowd out of the game, not put them more into it.

Most of all, you can’t be stupid and not be ready to play. The Knicks were coming off the biggest of wins against Miami on Sunday, but they knew the Pacers were looking for blood, and they got their quart of red in the first quarter as they ran out to a 35-17 lead. The Knicks did not put in the effort needed for an Eastern Conference Final affair.

“We were ill-prepared for the intensity of the first quarter,” said Jeff Van Gundy, who did not have his team ready. “The game was very easy for all [the Pacers] tonight. They are by far the best offensive team in the East. They were ready to play. We wasted a quarter in the first quarter. When you waste a quarter, you get beat.”

The Knicks wasted a strong offensive effort by Patrick Ewing (21 points). Ewing, though, would not move out to guard Rik Smits early, and that mistake was costly.

“A lot of our guys stepped up our games,” said Smits, who hit seven of 10 from the field on his way to 16 points. The Pacers owned a 14-5 rebound advantage after one quarter. By the time Van Gundy got Marcus Camby into the game, the Knicks were down 10 points.

These are not the same Pacers as last year, and the Knicks learned that the hard way. There’s still Reggie Miller, of course, but sharpshooting Austin Croshere was the best sixth man on the floor last night, not Camby, who tortured the Pacers last year in the playoffs. Camby was two for 9 from the field with eight rebounds. Croshere pumped in 22 points, including four of five from three-point land. He’s no Clarence Weatherspoon.

“We’re going to come out on Thursday and play better basketball,” guaranteed Camby. They can’t be much worse.

Croshere would be the Heat’s second-best offensive player. There are no disappearing Jamal Mashburn’s on this squad. They did not panic when the Knicks cut a 16-point lead to two early in the third.

The Pacers take their lead from Cool Hand Larry Bird, who made this cutting comment about the Knicks.

“It’s hard for me to be p—ed off at a team when I have more championship rings than they do,” he said. The Knicks have had no rings since ’73. Bird has three.

“To win this series,” Van Gundy said before the game, “we are going to have to win the rebounding war. It can’t be a shootout – an open shot for them, an open shot for us.”

Van Gundy was prophetic. The Knicks got hammered on the boards, 43-35, and paid the price, being outscored 18-9 on second chance points. Yo, Knicks – you might want to block out just a bit.

Bird’s Pacers made all the smart moves.

“The team is as focused as I’ve ever seen them,” Bird said.

He knows the Knicks lost Game 1 in Miami, too, but stole the second one.

“I’ve told them already, the second game of the series is going to be toughest. New York is going to regroup,” Bird said.